Add getSalt to projects api. Add action, GET_SALT, on Store
Projects module to make the api request and return the salt
string everywhere in the web app that generates an access grant.
The Wasm code which is used to create the access grant has been
changed to decode the salt as a base64 encoded string. The names
of the function calls in the changed Wasm code have also been
changed to ensure that access grant creation fails if JS access
grant worker code and Wasm code are not the same version.
https://github.com/storj/storj-private/issues/64
Change-Id: Ia2bc4cbadad84b066ca1882b042a3f0bb13c783a
98fed4bc30